Use LatencyInfoSwapPromise to track LatencyInfo through compositor

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index a832c184faca4deb60607d8d3356cde67e1995cc..d394ea8854041fbab15501a4ab94868ac1a1cc80 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -471,7 +471,9 @@ bool LayerTreeHostImpl::HaveTouchEventHandlersAt(gfx::Point viewport_point) {
 
 void LayerTreeHostImpl::SetLatencyInfoForInputEvent(
     const ui::LatencyInfo& latency_info) {
-  active_tree()->SetLatencyInfo(latency_info);
+  scoped_ptr<cc::SwapPromise> swap_promise(

[danakj, 2013/11/26 19:17:53]

don't need cc:: inside cc::

[Yufeng Shen (Slow to review), 2013/11/27 20:05:33]

Done.

+      new cc::LatencyInfoSwapPromise(latency_info));
+  active_tree()->QueueSwapPromise(swap_promise.Pass());
 }
 
 void LayerTreeHostImpl::TrackDamageForAllSurfaces(
@@ -1265,7 +1267,7 @@ CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() const {
   metadata.root_layer_size = active_tree_->ScrollableSize();
   metadata.min_page_scale_factor = active_tree_->min_page_scale_factor();
   metadata.max_page_scale_factor = active_tree_->max_page_scale_factor();
-  metadata.latency_info = active_tree_->GetLatencyInfo();
+  active_tree_->TakeLatencyInfo(&metadata.latency_info);
   if (top_controls_manager_) {
     metadata.location_bar_offset =
         gfx::Vector2dF(0.f, top_controls_manager_->controls_top_offset());
@@ -1424,7 +1426,6 @@ bool LayerTreeHostImpl::SwapBuffers(const LayerTreeHostImpl::FrameData& frame) {
     return false;
   }
   renderer_->SwapBuffers();
-  active_tree_->ClearLatencyInfo();
   active_tree()->FinishSwapPromises();
   return true;
 }